1a. Objectives (from AD-416):
Objective 1: Enhance the human bioactive properties of resistant starch and slowly digestible starch in commercial table rice (milled, brown, and colored) while maintaining sensory texture characteristics. Sub-Objective 1.1. In this sub-objective research will characterize the sensory characteristics related to resistant starch, slowly digestible starch, and the optimization of healthy starch in cooked rice. Sub-Objective 1.2. Under this sub-objective several methods to produce high-resistant rice starch in flour will be examined in a baked food product. Resistant starch has many colonic health-promoting properties, but often does not formulate well as an ingredient in baked foods. Objective 2: Enable new commercial functional food products using whole grain rice and rice co-products. Sub-Objective 2.1. In joint research with CrispTek research in this sub-objective will focus on adding resistant starch, fiber, and protein to current low-oil absorbing frying batters utilizing rice foods and co-products. Nutritionally-enriched baked and fried foods will be developed that sustain sensory quality. Sub-Objective 2.2. Healthier rice milk beverages and improvement of rice bran soluble protein extraction for food and beverage use will be developed. Sub-Objective 2.3. The proposed research will develop and compare several methods to produce unique rice prebiotics combined with phenolics from blueberry pomace and spent green tea. The effectiveness of each prebiotic will be evaluated utilizing in vitro fermentations and a mouse model for colonic health.
1b. Approach (from AD-416):
Rice varieties vary in amylose content that lead to differences in digestibility. Cooked table rice from different varieties will be evaluated for the amount of resistant, slowly digestible, and rapidly digestible starch based on in vitro digestion times. Thermal processes and physicochemical methods will be used to produce high resistant starch content in rice flour and starch, which will be tested as ingredients in baked foods. In collaboration with CrispTek, research will focus on adding resistant starch, fiber, and protein from rice foods and co-products to current low-oil absorbing frying batters. Nutritionally-enriched baked and fried foods will be developed with sustained or enhanced sensory qualities. Rice beverages will be developed that incorporate green technologies (e.g. focusing on raw materials and enzymatic treatments that do not rely upon previous stabilization). Lastly, methods will be evaluated to produce prebiotics from rice that include thermal and physiochemical methods and encapsulation technologies.
3. Progress Report:
Progress was made on the two objectives and their sub objectives, all of which fall under National Program 306, Quality and Utilization of Agricultural Products recognizes this research need as part of Problem Statement 1.C: New Bioactive Ingredients and Functional Foods. Processing loss has been minimized through enzymatic conversion of insoluble solids into soluble solids-contained in the crude beverage. Further enzymatic conversion and homogenization tests are underway to optimize soluble solids content in the crude beverage. Under Sub objective 1.1, significant progress was made in examining diverse starch fractions from high amylose rice starch varieties, in addition to a low and intermediate amylose rice. The sensory evaluation of the 24 cooked rice samples was performed at Southern Regional Research Center, New Orleans, Louisiana. Sensory evaluation was accomplished with a trained descriptive texture panel of twelve persons. They evaluated the intensity of each of fourteen texture attributes on each rice sample. There were statistically significant differences between rice varieties for 13 of the 14 texture attributes. The sensory texture information is being analyzed along with the physicochemical measurements to understand how high resistant starch rice impacts sensory texture. Under Sub objective 1.2, progress was made to develop extrusion methods necessary for high amylose rice flour and starch. Experiments are ongoing to utilize rice flour and modified starch (developed in Sub objective 2.1) with high resistant starch content as ingredients for extruded rice foods. Increasing the content of resistant starch can result in a number of positive health outcomes including lower serum glucose values after a meal. Under Sub objective 2.1, progress was made at reformulating rice batters for a number of baked foods. Resistant starch in rice is typically at low levels and requires enzymatic processing and heating/cooling steps to increase resistant starch amounts. A method was developed that converted normal rice starch to a starch with a high resistant starch content. The processed rice starch was added to rice-based food batters, which were evaluated for color, texture quality, and oil content. Completed studies on fried rice batters containing added resistant starch did not alter the benefits of lowered oil uptake and texture (hardness/crispness). The processed rice starch batter will be applicable to baked foods. Under Sub objective 2.2, significant progress was made at refining a chemical-free, green processing method and parameters in germinated, brown rice, crude, rice milk beverage wherein proteins and oils are apparently soluble, not precipitating out, nor requiring filtration. Processing loss has been minimized through enzymatic conversion into a fairly stable 15% soluble solids-containing crude beverage. Tests are underway establishing benchmarks regarding quality control measures required to validate the findings. Further enzymatic conversion and homogenization are required. ARS researchers at the Southern Regional Research Center, New Orleans, Louisiana, are examining bioactive (health promoting) compounds in colored rice samples in collaboration with researchers at the Dale Bumpers Rice Research Center (Stuttgart, Arkansas) and Lundberg Farms (Richvale, California). Natural bioactive compounds include total phenolics, anthocyanins, proanthocyanidins, and gamma-aminobutyric acid. Additionally, research is examining the effect of sprouted rice on increasing bioactive compounds for production of functional foods and beverages. Under Subobjective 2.3, progress was made developing methods necessary to produce an extruded prebiotic. High resistant starch rice flour and modified starch (developed in Sub objective 2.1) are being added as an ingredient during extrusion to produce prebiotics.
1. Cooked rice containing resistant starch improves colon health. Typically rice is viewed only as a source of starch with few health benefits. Several new rice varieties containing high amounts of resistant starch are being developed that are beneficial to health. An animal study determined the effects of high resistant starch rice on cholesterol (lowering) and the microbiome (colonic bacteria). The study was a collaboration between ARS researchers at the Dale Bumpers Rice Research Center in Stuttgart, Arkansas; Southern Regional Research Center in New Orleans, Louisiana; and Beltsville Agricultural Research Center, in Beltsville, Maryland. Cooked rice was incorporated into the animal diets utilizing low, medium, and high resistant starch rice varieties. Results indicate rice containing high resistant starch content improves colon health through increased production of short-chain fatty acids. Data indicating improved colonic health and lowered cholesterol levels due to high resistant starch rice will provide valuable information about the nutritional benefits of rice consumption to consumers, stakeholders and farmers.
2. Rice resistant starch creates healthier food batters. ARS researchers at the Southern Regional Research Center, New Orleans, Louisiana, are developing healthier batters for fried and baked foods. One way of developing a healthier batter is to add fiber; however the fiber can have adverse effects on batter texture, color, and oil absorption. Another approach is to increase the amount of resistant starch in rice starch. A method was developed, which converted normal rice starch to a starch with a high resistant starch content. The high resistant rice starch was added to rice-based food batters, which were evaluated for color, texture quality, and oil content. Results showed that batters containing added resistant starch maintained the benefits of lowered oil uptake and had desirable texture (hardness/crispness). Additionally, fried onion strips with rice batters containing high resistant starch retained good sensory characteristics. This research will assist stakeholders that are developing health-promoting food ingredients that make commercial products for consumers seeking healthier fried and baked foods.
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